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SubjectRe: [PATCH V3 5/5] drm/vkms: Add support for writeback
On Tue, Jun 25, 2019 at 10:39:03PM -0300, Rodrigo Siqueira wrote:
> This patch implements the necessary functions to add writeback support
> for vkms. This feature is useful for testing compositors if you don't
> have hardware with writeback support.
>
> Change in V3 (Daniel):
> - If writeback is enabled, compose everything into the writeback buffer
> instead of CRC private buffer.
> - Guarantees that the CRC will match exactly what we have in the
> writeback buffer.
>
> Change in V2:
> - Rework signal completion (Brian)
> - Integrates writeback with active_planes (Daniel)
> - Compose cursor (Daniel)
>
> Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> ---
> drivers/gpu/drm/vkms/Makefile | 9 +-
> drivers/gpu/drm/vkms/vkms_composer.c | 16 ++-
> drivers/gpu/drm/vkms/vkms_drv.c | 4 +
> drivers/gpu/drm/vkms/vkms_drv.h | 8 ++
> drivers/gpu/drm/vkms/vkms_output.c | 10 ++
> drivers/gpu/drm/vkms/vkms_writeback.c | 141 ++++++++++++++++++++++++++
> 6 files changed, 185 insertions(+), 3 deletions(-)
> create mode 100644 drivers/gpu/drm/vkms/vkms_writeback.c
>
> diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
> index 0b767d7efa24..333d3cead0e3 100644
> --- a/drivers/gpu/drm/vkms/Makefile
> +++ b/drivers/gpu/drm/vkms/Makefile
> @@ -1,4 +1,11 @@
> # SPDX-License-Identifier: GPL-2.0-only
> -vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o vkms_composer.o
> +vkms-y := \
> + vkms_drv.o \
> + vkms_plane.o \
> + vkms_output.o \
> + vkms_crtc.o \
> + vkms_gem.o \
> + vkms_composer.o \
> + vkms_writeback.o
>
> obj-$(CONFIG_DRM_VKMS) += vkms.o
> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> index 8126aa0f968f..2317803e7320 100644
> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -157,16 +157,17 @@ void vkms_composer_worker(struct work_struct *work)
> struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> struct vkms_composer *primary_composer = NULL;
> struct vkms_composer *cursor_composer = NULL;
> + bool crc_pending, wb_pending;

I'm not seeing how you schedule this work for writeback if there's no crc
enabled. Does that work?
> void *vaddr_out = NULL;
> u32 crc32 = 0;
> u64 frame_start, frame_end;
> - bool crc_pending;
> int ret;
>
> spin_lock_irq(&out->composer_lock);
> frame_start = crtc_state->frame_start;
> frame_end = crtc_state->frame_end;
> crc_pending = crtc_state->crc_pending;
> + wb_pending = crtc_state->wb_pending;
> crtc_state->frame_start = 0;
> crtc_state->frame_end = 0;
> crtc_state->crc_pending = false;
> @@ -188,9 +189,12 @@ void vkms_composer_worker(struct work_struct *work)
> if (!primary_composer)
> return;
>
> + if (wb_pending)
> + vaddr_out = crtc_state->active_writeback;
> +
> ret = compose_planes(&vaddr_out, primary_composer, cursor_composer);
> if (ret) {
> - if (ret == -EINVAL)
> + if (ret == -EINVAL && !wb_pending)
> kfree(vaddr_out);
> return;
> }
> @@ -203,6 +207,14 @@ void vkms_composer_worker(struct work_struct *work)
> while (frame_start <= frame_end)
> drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
>
> + if (wb_pending) {
> + drm_writeback_signal_completion(&out->wb_connector, 0);
> + spin_lock_irq(&out->composer_lock);
> + crtc_state->wb_pending = false;
> + spin_unlock_irq(&out->composer_lock);
> + return;
> + }
> +
> kfree(vaddr_out);
> }
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index ac790b6527e4..152d7de24a76 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -30,6 +30,10 @@ bool enable_cursor;
> module_param_named(enable_cursor, enable_cursor, bool, 0444);
> MODULE_PARM_DESC(enable_cursor, "Enable/Disable cursor support");
>
> +bool enable_writeback;
> +module_param_named(enable_writeback, enable_writeback, bool, 0444);
> +MODULE_PARM_DESC(enable_writeback, "Enable/Disable writeback connector");
> +
> static const struct file_operations vkms_driver_fops = {
> .owner = THIS_MODULE,
> .open = drm_open,
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index fc6cda164336..9ff2cd4ebf81 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -7,6 +7,7 @@
> #include <drm/drm.h>
> #include <drm/drm_gem.h>
> #include <drm/drm_encoder.h>
> +#include <drm/drm_writeback.h>
> #include <linux/hrtimer.h>
>
> #define XRES_MIN 20
> @@ -19,6 +20,7 @@
> #define YRES_MAX 8192
>
> extern bool enable_cursor;
> +extern bool enable_writeback;
>
> struct vkms_composer {
> struct drm_framebuffer fb;
> @@ -52,9 +54,11 @@ struct vkms_crtc_state {
> int num_active_planes;
> /* stack of active planes for crc computation, should be in z order */
> struct vkms_plane_state **active_planes;
> + void *active_writeback;
>
> /* below three are protected by vkms_output.composer_lock */
> bool crc_pending;
> + bool wb_pending;
> u64 frame_start;
> u64 frame_end;
> };
> @@ -63,6 +67,7 @@ struct vkms_output {
> struct drm_crtc crtc;
> struct drm_encoder encoder;
> struct drm_connector connector;
> + struct drm_writeback_connector wb_connector;
> struct hrtimer vblank_hrtimer;
> ktime_t period_ns;
> struct drm_pending_vblank_event *event;
> @@ -147,4 +152,7 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
> /* Composer Support */
> void vkms_composer_worker(struct work_struct *work);
>
> +/* Writeback */
> +int enable_writeback_connector(struct vkms_device *vkmsdev);
> +
> #endif /* _VKMS_DRV_H_ */
> diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> index fb1941a6522c..aea1d4410864 100644
> --- a/drivers/gpu/drm/vkms/vkms_output.c
> +++ b/drivers/gpu/drm/vkms/vkms_output.c
> @@ -84,6 +84,16 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> goto err_attach;
> }
>
> + if (enable_writeback) {
> + ret = enable_writeback_connector(vkmsdev);
> + if (!ret) {
> + output->composer_enabled = true;
> + DRM_INFO("Writeback connector enabled");
> + } else {
> + DRM_ERROR("Failed to init writeback connector\n");
> + }
> + }
> +
> drm_mode_config_reset(dev);
>
> return 0;
> diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c b/drivers/gpu/drm/vkms/vkms_writeback.c
> new file mode 100644
> index 000000000000..34dad37a0236
> --- /dev/null
> +++ b/drivers/gpu/drm/vkms/vkms_writeback.c
> @@ -0,0 +1,141 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +
> +#include "vkms_drv.h"
> +#include <drm/drm_writeback.h>
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_gem_framebuffer_helper.h>
> +
> +static const u32 vkms_wb_formats[] = {
> + DRM_FORMAT_XRGB8888,
> +};
> +
> +static const struct drm_connector_funcs vkms_wb_connector_funcs = {
> + .fill_modes = drm_helper_probe_single_connector_modes,
> + .destroy = drm_connector_cleanup,
> + .reset = drm_atomic_helper_connector_reset,
> + .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +};
> +
> +static int vkms_wb_encoder_atomic_check(struct drm_encoder *encoder,
> + struct drm_crtc_state *crtc_state,
> + struct drm_connector_state *conn_state)
> +{
> + struct drm_framebuffer *fb;
> + const struct drm_display_mode *mode = &crtc_state->mode;
> +
> + if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
> + return 0;
> +
> + fb = conn_state->writeback_job->fb;
> + if (fb->width != mode->hdisplay || fb->height != mode->vdisplay) {
> + DRM_DEBUG_KMS("Invalid framebuffer size %ux%u\n",
> + fb->width, fb->height);
> + return -EINVAL;
> + }
> +
> + if (fb->format->format != DRM_FORMAT_XRGB8888) {
> + struct drm_format_name_buf format_name;
> +
> + DRM_DEBUG_KMS("Invalid pixel format %s\n",
> + drm_get_format_name(fb->format->format,
> + &format_name));
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static const struct drm_encoder_helper_funcs vkms_wb_encoder_helper_funcs = {
> + .atomic_check = vkms_wb_encoder_atomic_check,
> +};
> +
> +static int vkms_wb_connector_get_modes(struct drm_connector *connector)
> +{
> + struct drm_device *dev = connector->dev;
> +
> + return drm_add_modes_noedid(connector, dev->mode_config.max_width,
> + dev->mode_config.max_height);
> +}

Do we need a mode for writeb connector? Is that used by userspace to
figure out the max size for writeback?

> +
> +static int vkms_wb_prepare_job(struct drm_writeback_connector *wb_connector,
> + struct drm_writeback_job *job)
> +{
> + struct vkms_gem_object *vkms_obj;
> + struct drm_gem_object *gem_obj;
> + int ret;
> +
> + if (!job->fb)
> + return 0;

Can this happen?

> +
> + gem_obj = drm_gem_fb_get_obj(job->fb, 0);
> + ret = vkms_gem_vmap(gem_obj);
> + if (ret) {
> + DRM_ERROR("vmap failed: %d\n", ret);
> + return ret;
> + }
> +
> + vkms_obj = drm_gem_to_vkms_gem(gem_obj);
> + job->priv = vkms_obj->vaddr;
> +
> + return 0;
> +}
> +
> +static void vkms_wb_cleanup_job(struct drm_writeback_connector *connector,
> + struct drm_writeback_job *job)
> +{
> + struct drm_gem_object *gem_obj;
> +
> + if (!job->fb)
> + return;

Same here?

> +
> + gem_obj = drm_gem_fb_get_obj(job->fb, 0);
> + vkms_gem_vunmap(gem_obj);
> +}
> +
> +static void vkms_wb_atomic_commit(struct drm_connector *conn,
> + struct drm_connector_state *state)
> +{
> + struct vkms_device *vkmsdev = drm_device_to_vkms_device(conn->dev);
> + struct vkms_output *output = &vkmsdev->output;
> + struct drm_writeback_connector *wb_conn = &output->wb_connector;
> + struct drm_connector_state *conn_state = wb_conn->base.state;
> + struct vkms_crtc_state *crtc_state = output->composer_state;
> +
> + if (!conn_state)
> + return;
> +
> + if (!conn_state->writeback_job || !conn_state->writeback_job->fb) {
> + DRM_DEBUG_DRIVER("Disable writeback\n");
> + return;
> + }

All three checks above sound like helpers should take care of this?

> +
> + spin_lock_irq(&output->composer_lock);
> + crtc_state->active_writeback = conn_state->writeback_job->priv;
> + crtc_state->wb_pending = true;
> + spin_unlock_irq(&output->composer_lock);
> + drm_writeback_queue_job(wb_conn, state);
> +}
> +
> +static const struct drm_connector_helper_funcs vkms_wb_conn_helper_funcs = {
> + .get_modes = vkms_wb_connector_get_modes,
> + .prepare_writeback_job = vkms_wb_prepare_job,
> + .cleanup_writeback_job = vkms_wb_cleanup_job,
> + .atomic_commit = vkms_wb_atomic_commit,
> +};
> +
> +int enable_writeback_connector(struct vkms_device *vkmsdev)
> +{
> + struct drm_writeback_connector *wb = &vkmsdev->output.wb_connector;
> +
> + vkmsdev->output.wb_connector.encoder.possible_crtcs = 1;
> + drm_connector_helper_add(&wb->base, &vkms_wb_conn_helper_funcs);
> +
> + return drm_writeback_connector_init(&vkmsdev->drm, wb,
> + &vkms_wb_connector_funcs,
> + &vkms_wb_encoder_helper_funcs,
> + vkms_wb_formats,
> + ARRAY_SIZE(vkms_wb_formats));
> +}

Overall looks like good approach.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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